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FROMLIST: userfaultfd/shmem: fix minor fault page leak

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This fix is analogous to Peter Xu's fix for hugetlb [0]. If we don't
put_page() after getting the page out of the page cache, we leak the
reference.

The fix can be verified by checking /proc/meminfo and running the
userfaultfd selftest in shmem mode. Without the fix, we see MemFree /
MemAvailable steadily decreasing with each run of the test. With the
fix, memory is correctly freed after the test program exits.

Fixes: 00da60b9d0a0 ("userfaultfd: support minor fault handling for shmem")
Signed-off-by: Axel Rasmussen <axelrasmussen@google.com>
Reviewed-by: Peter Xu <peterx@redhat.com>

Signed-off-by: Lokesh Gidra <lokeshgidra@google.com>
Link: https://lore.kernel.org/patchwork/patch/1400686/
Bug: 160737021
Bug: 169683130
Change-Id: I599f1434e24fce6e31d0d73c7f9c4714e9875b63
This commit is contained in:
Axel Rasmussen 2021-03-22 13:48:35 -07:00 committed by Todd Kjos
parent 26d1bb8087
commit 02732576b1
1 changed files with 1 additions and 0 deletions
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1
mm/shmem.c
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@ -1831,6 +1831,7 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index,
if (page && vma && userfaultfd_minor(vma)) {
unlock_page(page);
put_page(page);
*fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
return 0;
}